La Niña Points to Warm and Dry Winter
By Daniel Huckaby
For North Texas, the winter of 2009-2010 was among the coldest and snowiest on record. El Niño does not guarantee heavy snow, but the strong El Niño event last winter was a major contributor to both the increased precipitation and the colder than normal temperatures. Despite its strength, the El Niño event came to an abrupt end. The equatorial Pacific is now 4 to 6 degrees Fahrenheit colder than it was 12 months ago, marking a rapid transition to La Niña.
This periodic flip-flopping of sea surface temperatures is known as the El Niño-Southern Oscillation (ENSO). The Pacific Ocean covers one third of the earth’s surface, and the ocean’s widest breadth is at the equator, where water temperatures determine the ENSO phase. This is an enormous surface area, where even slight temperature changes can significantly affect the heat content of the air above it, resulting in a cascading effect of altering wind and weather patterns, even in far-reaching parts of the globe (see picture below).
During La Niña, North Texas winters are typically warmer and drier than normal. The current La Niña is moderate to strong, which history has shown further reduces winter precipitation totals. Unfortunately for kids (and other snow lovers) this makes a repeat of last winter’s snowfall very unlikely. Since continuous weather records were first kept in North Texas in the late 1800s, there has never been a winter without some wintry precipitation. However, many years have had little to no measurable snowfall, particularly during La Niña.
More likely than heavy snow is a continuation of precipitation deficits that have accumulated since September. As a result, drought conditions across the region are expected to persist in Central and South Texas, with a likely expansion of the drought further into North Texas. In addition, the most active fire seasons of the last decade were during La Niña conditions, and the winter of 2010-2011 is expected to follow suit.
For more information about the El Niño/Southern Oscillation, visit our ENSO webpage at http://www.weather.gov/fortworth/?n=enso
For information about the ongoing drought, visit our drought information page at http://www.weather.gov/fortworth/?n=drought
Texas Thunderbolt Winter 2011, National Weather Service Forth Worth Office
